Intravitreal injection of vancomycin in experimental staphylococcal endophthalmitis

Consensus and controversies in the science of endophthalmitis management: Basic research and clinical perspectives

Infectious endophthalmitis is a severe intraocular infection caused by bacteria, or less commonly by fungi. It can occur after penetrating eye procedures, trauma, or the spread of infection from contiguous structures or via emboli from distant organs. Because of the time-critical nature of the treatment, endophthalmitis is treated with the clinical diagnosis and modified by the microbiological report of the intraocular contents. The current strategy for managing endophthalmitis relies on pre-clinical literature, case series, and one large multi-center randomized clinical trial on post-cataract surgery endophthalmitis. Culture-susceptibility of the microorganisms from undiluted vitreous guides the definitive treatment in non-responsive cases. Strategies to reduce the incidence of endophthalmitis after penetrating eye procedures have been developed concurrently with refined means of treatment. Despite these advances, outcomes remain poor for many patients. Although consensus articles have been published on managing endophthalmitis, treatment patterns vary, and controversies remain. These include (1) the use of newer methods for early and precise microbiological diagnosis; (2) the choice of intravitreal antibiotics; (3) the need for systemic therapy; (4) early and complete vitrectomy. Here, we review the current consensus and address controversies in diagnosing and managing endophthalmitis. This review is intended to familiarize physicians and ophthalmologists with different aspects of endophthalmitis management to make informed decisions.

Bifidobacterium promotes retinal ganglion cell survival by regulating the balance of retinal glial cells

INTRODUCTION

Optic nerve injury is a leading cause of irreversible blindness worldwide. The retinal ganglion cells (RGCs) and their axons cannot be regenerated once damaged. Therefore, reducing RGC damage is crucial to prevent blindness. Accordingly, we aimed to investigate the potential influence of the gut microbiota on RGC survival, as well as the associated action mechanisms.

METHODS

We evaluated the effects of microbiota, specifically Bifidobacterium, on RGC. Optic nerve crush (ONC) was used as a model of optic nerve injury. Vancomycin and Bifidobacterium were orally administered to specific pathogen-free (SPF) mice.

RESULTS

Bifidobacterium promoted RGC survival and optic nerve regeneration. The administration of Bifidobacterium inhibited microglia activation but promoted Müller cell activation, which was accompanied by the downregulation of inflammatory cytokines and upregulation of neurotrophic factors and retinal ERK/Fos signaling pathway activation.

CONCLUSIONS

Our study demonstrates that Bifidobacterium-induced changes in intestinal flora promote RGC survival. The protective effect of Bifidobacterium on RGC can be attributed to the inhibition of microglia activation and promotion of Müller cell activation and the secondary regulation of inflammatory and neurotrophic factors.

Intravitreal injection of povidone-iodine for the treatment of vancomycin-resistant Enterococcus faecalis endophthalmitis in rabbit eyes

The aim of this study was to investigate the efficacy of intravitreal povidone-iodine (PI) in the treatment of vancomycin-resistant Enterococcus faecalis (VRE) endophthalmitis. Fifty New Zealand white rabbits were divided into 5 groups (n = 10 in each group). After the induction of endophthalmitis using VRE (minimum inhibitory concentration [MIC] ≥ 40 μg/mL) in the right eye, Group A, B, C, and D received intravitreal injections of 0.1% PI, 0.3% PI, 0.05% vancomycin, and 0.5% vancomycin, respectively. Eyes in Group E were used as controls. Fundus photography, vitreous culture, electroretinography (ERG), and histologic examinations of the retina were conducted on day 14. A marked improvement in endophthalmitis was observed in Group A, B, C and D, compared to Group E. Fundus photographs showed mild vitreous opacities in Group A and B, and moderate vitreous opacity in Group C. All eyes in Group D had a clear vitreous. In vitreous culture, bacterial growth was found in 6 eyes (100, 200, 200, 400, 500, and 500 colony-forming units) in Group C, but not in Groups A, B, or D. ERG and histological examination also indicated intraocular damage in Group C. Our results show that intravitreal injection of PI, even at low concentrations, was effective for treatment of VRE endophthalmitis, although some vitreous opacity remained. Intravitreal vancomycin injection was also useful to treat resistant strains, if used at a higher concentration within the safety threshold.

Genotypic and Phenotypic Antibiotic Resistance in Staphylococcus Epidermidis Endophthalmitis

BACKGROUND AND OBJECTIVE

To evaluate antibiotic resistance patterns in Staphylococcus epidermis endophthalmitis isolates, identify antibiotic resistance genes, and compare this to their phenotypic resistance.

MATERIALS AND METHODS

Retrospective case series of S. epidermidis isolates from January 2012 to December 2017. Phenotypic resistance was determined from minimum inhibitory concentration values. Genotypic resistance was determined from DNA microarray. The relationship between these was analyzed using Cohen's kappa and predictive value.

RESULTS

Seventy-five isolates were included. More than 60% were resistant to methicillin and erythromycin. Approximately 60% possessed the resistance genes for methicillin and erythromycin, and 25% for clindamycin. There was near perfect agreement between genotype and phenotype for erythromycin and methicillin (kappa = 0.88 and 0.89, respectively). Approximately 98% (P < 0.0001) of isolates with erythromycin and methicillin resistance genes and 90% (P = 0.0006) with clindamycin resistance genes were phenotypically resistant to those antibiotics. None were resistant to vancomycin.

CONCLUSION

The relationship between genotypic and phenotypic antibiotic resistance highlights that resistance may be polygenic, and genes may be silent. [Ophthalmic Surg Lasers Imaging Retina. 2020;51:S13-S16.].

Antimicrobial resistance of ocular microbes and the role of antimicrobial peptides

Isolation of antimicrobial-resistant microbes from ocular infections may be becoming more frequent. Infections caused by these microbes can be difficult to treat and lead to poor outcomes. However, new therapies are being developed which may help improve clinical outcomes. This review examines recent reports on the isolation of antibiotic-resistant microbes from ocular infections. In addition, an overview of the development of some new antibiotic therapies is given. The recent literature regarding antibiotic use and resistance, isolation of antibiotic-resistant microbes from ocular infections and the development of potential new antibiotics that can be used to treat these infections was reviewed. Ocular microbial infections are a global public health issue as they can result in vision loss which compromises quality of life. Approximately 70 per cent of ocular infections are caused by bacteria including Chlamydia trachomatis, Staphylococcus aureus, and Pseudomonas aeruginosa and fungi such as Candida albicans, Aspergillus spp. and Fusarium spp. Resistance to first-line antibiotics such as fluoroquinolones and azoles has increased, with resistance of S. aureus isolates from the USA to fluoroquinolones reaching 32 per cent of isolates and 35 per cent being methicillin-resistant (MRSA). Lower levels of MRSA (seven per cent) were isolated by an Australian study. Antimicrobial peptides, which are broad-spectrum alternatives to antibiotics, have been tested as possible new drugs. Several have shown promise in animal models of keratitis, especially treating P. aeruginosa, S. aureus or C. albicans infections. Reports of increasing resistance of ocular isolates to mainstay antibiotics are a concern, and there is evidence that for ocular surface disease this resistance translates into worse clinical outcomes. New antibiotics are being developed, but not by large pharmaceutical companies and mostly in university research laboratories and smaller biotech companies. Antimicrobial peptides show promise in treating keratitis.

Endophthalmitis caused by Gram-positive organisms with reduced vancomycin susceptibility: literature review and options for treatment

BACKGROUND

Endophthalmitis caused by Gram-positive organisms with reduced vancomycin susceptibility and/or resistance is an important clinical issue worldwide.

PURPOSE

To review the published literature on endophthalmitis caused by Gram-positive organisms with reduced vancomycin susceptibility and/or vancomycin resistance.

METHODS

The data were analysed from a PubMed search of endophthalmitis cases caused by Gram-positive organisms with reported reduced vancomycin susceptibility and/or vancomycin resistance from 1990 to 2015.

RESULTS

From 18 publications identified, a total of 27 endophthalmitis cases caused by Gram-positive organisms with reduced vancomycin susceptibility and/or vancomycin resistance were identified. The aetiologies of endophthalmitis were exogenous in 19/27 cases (11 post-cataract surgery, 2 post-penetrating keratoplasty, 1 post-glaucoma surgery, 4 post-open globe injury, 1 post-intravitreal injection of ranibizumab), and endogenous in 4/24 cases; no details were available about the four remaining patients. The causative organisms included Enterococcus species (7/27), coagulase-negative staphylococci (4/27), Staphylococcus aureus (4/27), Bacillus species (4/27), Streptococcus species (3/27), Leuconostoc species (3/27), Staphylococcus hominis (1/27), and unidentified Gram-positive cocci (1/27). Visual acuity of 20/400 or better at the final follow-up was recorded in 10/26 patients (38.5%; data were not available for one patient). Treatment options include fluoroquinolones, penicillin, cephalosporins, tetracyclines, and oxazolidinones.

CONCLUSIONS

In the current study, visual acuity outcomes were generally poor. Enterococcus and Staphylococcus species were the most common organisms reported and postoperative endophthalmitis after cataract surgery was the most common clinical setting.

Pharmacokinetics of intravitreal antibiotics in endophthalmitis

Intravitreal antibiotics are the mainstay of treatment in the management of infectious endophthalmitis. Basic knowledge of the commonly used intravitreal antibiotics, which includes their pharmacokinetics, half-life, duration of action and clearance, is essential for elimination of intraocular infection without any iatrogenic adverse effect to the ocular tissue. Various drugs have been studied over the past century to achieve this goal. We performed a comprehensive review of the antibiotics which have been used for intravitreal route and the pharmacokinetic factors influencing the drug delivery and safety profile of these antibiotics. Using online resources like PubMed and Google Scholar, articles were reviewed. The articles were confined to the English language only. We present a broad overview of pharmacokinetic concepts fundamental for use of intravitreal antibiotics in endophthalmitis along with a tabulated compendium of the intravitreal antibiotics using available literature. Recent advances for increasing bioavailability of antibiotics to the posterior segment with the development of controlled drug delivery devices are also described.

Interaction of intravitreal combination drugs and the effect on the targeted site

BACKGROUND

After evaluating experimentally the diffusion processes in the retina using peroxidase as a tracer material (previously published work), we found that junctional complexes of the retinal pigment epithelium and retinal capillaries were the major impediment to free diffusion between the retina and choroidal-retinal blood vessels. These experiments indicated that to achieve high therapeutic concentrations of medications inside the eye, it was necessary to administer them by intravitreal injection. Soon after initial experimental work the necessity of combining antibiotics or antibiotics with steroids became obvious. As the use of intravitreal injection grew over the last 2 decades, so did the concept of combination therapy.

METHODS

This review describes potential causes of drug-drug interaction and the rationale for combination therapy when injected into the vitreous cavity, encompassing publications between 1971 and 2008.

RESULTS

We describe the conditions that can cause physical-chemical interactions between the medications and the need for combination therapy for treatment of various intraocular disease processes.

CONCLUSIONS

The intravitreal injection of medication and their combinations has become a part of standard care for many diseases of the retina and choroid. This article reviews the potential interaction of nontoxic doses of medications when injected simultaneously in the vitreous cavity, and disease processes that are now treated with these combination therapies.

Intravitreal injection of therapeutic agents

BACKGROUND

Intravitreal injection (IVI) with administration of various pharmacological agents is a mainstay of treatment in ophthalmology for endopthalmitis, viral retinitis, age-related macular degeneration, cystoid macular edema, diabetic retinopathy, uveitis, vascular occlusions, and retinal detachment. The indications and therapeutic agents are reviewed in this study.

METHODS

A search of the English, German, and Spanish language MEDLINE database was conducted. A total of 654 references spanning the period through early 2008 were individually evaluated.

RESULTS

The advantage of the IVI technique is the ability to maximize intraocular levels of medications and to avoid the toxicities associated with systemic treatment. Intravitreal injection has been used to deliver several types of pharmacological agents into the vitreous cavity: antiinfective and antiinflammatory medications, immunomodulators, anticancer agents, gas, antivascular endothelial growth factor, and several others. The goal of this review is to provide a detailed description of the properties of numerous therapeutic agents that can be delivered through IVI, potential complications of the technique, and recommendations to avoid side effects.

CONCLUSION

The IVI technique is a valuable tool that can be tailored to the disease process of interest based on the pharmacological agent selected. This review provides the reader with a comprehensive summary of the IVI technique and its multitude of uses.

[Intravitreal injection of antibiotics in endophthalmitis]

Early diagnosis and appropriate treatment with intravitreous antibiotics are the most important factors for the successful management of endophthalmitis. The intraocular concentration of antibiotics after intravitreous injection is far greater than that achieved by any other modality. The organisms in postoperative endophthalmitis are usually Gram-positive cocci and less commonly Gram-negative bacteria. Drug combinations are necessary to cover the full range of bacteria causing endophthalmitis. Vancomycin (1 mg/0.1 ml) is considered the drug of choice for Gram-positive organisms. Controversy remains concerning the best choice against Gram-negative bacteria. Aminoglycosides (amikacin, 0.4 mg/0.1 ml) have traditionally been recommended for Gram-negative coverage. However, because of their possible role in macular toxicity, recent trends have shifted to using ceftazidime (2.25 mg/0.1 ml) in combination with vancomycin.

Endophthalmitis: a review of current evaluation and management

PURPOSE

To review the current state of evaluation and management of various forms of endophthalmitis.

METHODS

A review of the literature is included, encompassing endophthalmitis occurring after ocular surgeries, intravitreal injection, trauma, and systemic infection. Based on this review, current principles and techniques for evaluating and treating these forms of endophthalmitis are discussed.

RESULTS

Postoperative endophthalmitis after cataract surgery is the most common presentation. Conclusions from the Endophthalmitis Vitrectomy Study (EVS) remain a foundation for management of postcataract surgery endophthalmitis, notably prompt intravitreal antibiotic administration after vitreous sampling, with consideration for pars plana vitrectomy in severe cases. The potential impact of advances since the EVS, such as oral fourth generation fluoroquinolones and new vitrectomy techniques, are also discussed. The management of postcataract endophthalmitis is compared and contrasted to endophthalmitis occurring after other ocular surgeries, intravitreal injection, trauma, and systemic infection. Although some principles remain common, treatment rationales differ with other forms of endophthalmitis based on differing clinical circumstances, such as the virulence of organisms that are frequently encountered.

CONCLUSIONS

Endophthalmitis is a serious, potentially vision threatening condition which can present in various settings. Prompt recognition and treatment are key in maximizing outcomes.

INTRAVITREAL TOXICITY OF MOXIFLOXACIN

PURPOSE

To assess the retinal toxicity of various concentrations of intravitreally administered moxifloxacin, a fourth-generation fluoroquinolone.

METHODS

Ten New Zealand albino rabbits were divided into five groups. The initial concentration of moxifloxacin (400 mg/250 mL) was titrated using 5% dextrose solution to concentrations (320 microg/0.1 mL, 160 microg/0.1 mL, 100 microg/0.1 mL, and 50 microg/0.1 mL) that were injected intravitreally into 1 eye of each rabbit. Two control eyes were injected intravitreally with 0.1 mL of 5% dextrose solution. All animals were examined before and after injection by indirect ophthalmoscopy and slit-lamp biomicroscopy; electroretinography (ERG) was performed on all animals. The animals were killed, and their eyes were enucleated and examined with light microscopy.

RESULTS

Remarkable decreases in ERG findings were noted in the group injected with moxifloxacin at a concentration of 320 microg/0.1 mL. No meaningful ERG changes were observed in eyes injected with moxifloxacin at other concentrations. There were no signs of retinal toxicity during slit-lamp examination, indirect ophthalmoscopy, or light microscopy in any eyes injected with moxifloxacin concentrations of < or =160 microg/0.1 mL.

CONCLUSIONS

Intravitreal injection of moxifloxacin at a concentration of < or =160 microg/0.1 mL appeared nontoxic in the rabbit eye.

The intraocular dynamics of vancomycin hydrochloride ophthalmic ointment (TN-011) in rabbits

The intraocular dynamics of 1% vancomycin hydrochloride (VCM) ophthalmic ointment (TN-011) in rabbits was investigated. The animals used in the study were 42 pigmented rabbits with normal eyes (normal group) and 17 pigmented rabbits with Bacillus subtilis-infected eyes (BS group). The infection in the BS group was induced by a method previously established by the authors. Fifty milligrams of a 1% VCM ophthalmic ointment was administered into the cul-de-sacs of the animals' eyes unilaterally in both groups. Serum, bulbar conjunctiva (only from the normal group), cornea, iris-ciliary body, and vitreous were collected 15, 30, 60, 120, and 240 min after the drug administration as samples. Drug concentration was measured by the bioassay method. In the normal group, VCM in the bulbar conjunctiva reached a maximum concentration (98.98 +/- 46.48 microg/g) at 30 min, and decreased to a level below the detection limit at 240 min. The maximum concentration of VCM in the cornea (12.04 +/- 4.73 microg/g) was observed at 30 min. VCM was not detected in the aqueous humour, iris-ciliary body, vitreous, or serum in the normal group at any point. In the BS group, the maximum concentration of VCM was 25.60 +/- 11.01 microg/g in the cornea 15 min after drug administration, and 5.18 +/- 2.60 microg/ml in the aqueous humour at 30 min. VCM in the aqueous humor could be detected (0.37 +/- 0.19 microg/ml) even after 240 min. VCM was not detected in the iris-ciliary body, vitreous, or serum at any point. The intraocular dynamics of 1% VCM ophthalmic ointment (TN-011) revealed that VCM reached the estimated effective concentrations in the aqueous humour as well as extraocular tissues of Bacillus subtilis-infected rabbit eyes.

Antibiotic therapy in post-operative endophthalmitis

Endophthalmitis following routine cataract surgery is a rare but potentially devastating complication resulting in severe vision loss. Various prophylaxis treatments have been tried. However, none have been demonstrated to completely eliminate the risk. The Endophthalmitis Vitrectomy Study (EVS) helped establish clinical guidelines in the treatment of post-operative endophthalmitis in a prospective, randomized, multicenter trial. The strength and limitation of the study will be discussed as well as the current knowledge of the pharmacokinetics of intravitreous injection of antibiotics. Additionally, the common pathologic organisms, the use of antibiotic therapy, steroids, and vitrectomy will be discussed.

Pharmacokinetics of 0.5 mg of a single and a multiple dose of intravitreal vancomycin in infected rabbit eyes

The purpose of this study was to determine the pharmacokinetics governing distribution and elimination of 0.5 mg of intravitreal vancomycin in a single dose and in a multiple therapeutic regime in infected rabbit eyes. A total of 96 rabbits was injected with approximately 200 CFU of S. aureus intravitreally. Four days later, a single dose of 0.5 mg of vancomycin was administered to Group I (n=36). Group II (n=60) was injected with a maximum of 4 doses of 0.5 mg every 36 hr. Four animals were sacrificed at different time points in each group. Samples of vitreous, aqueous and blood were taken from each animal for analyses by HPLC. These results were evaluated using the RSTRIP program. High vancomycin concentrations were demonstrated in the vitreous of Group I, with a calculated half-life of 12 hr. In Group II, vancomycin levels were within the therapeutic range during the entire experiment. There was minimal accumulation of the drug, and the half-life did not seem to be longer with multiple doses. In conclusion, the pharmacokinetics do not change significantly when a multidose regime is used compared with a single dose. Therapeutic intravitreal concentrations of vancomycin can be achieved by using repeated doses of 0.5 mg of vancomycin.

Clostridium beijerinckii endophthalmitis secondary to penetrating ocular injury

Endophthalmitis occurs in five to 10% of injuries involving intraocular foreign bodies. A 52 year old abattoir worker sustained such penetrating ocular trauma and developed fulminant endophthalmitis. Clostridium beijerinckii was isolated from the vitreous humor. Intravitreal vancomycin and amikacin and intravenous penicillin and clindamycin were given. Despite therapeutic vancomycin and amikacin levels in the vitreous, vision was lost and enucleation was ultimately required.

Pharmacokinetics of intravitreal vancomycin in normal and infected rabbit eyes

The purpose of this study was to determine the pharmacokinetics governing the distribution and elimination of intravitreally injected vancomycin in normal and infected rabbit eyes. Two groups each of 36 pigmented animals were used. Group 1 served as control. In Group 2, experimental endophthalmitis was induced in the right vitreous by inoculation with Staphylococcus aureus. Once endophthalmitis developed, a vancomycin solution was injected. Four animals from each group were killed at nine time points post-injection, the vitreous and aqueous were removed, and blood samples were taken for HPLC analysis. Data analysis was performed using the RSTRIP program. The half-lives were 69 hours in normal vitreous and 14.53 hours in infected vitreous. Therapeutic drug levels were present in the vitreous 84 hours post-injection in all eyes; they were detected from 2 to 48 hours in normal aqueous but at lower levels in the infected ones. Kv and Ca/Cv ratios suggested that the primary route of elimination was across the retina and the anterior chamber in normal eyes, and via the retina in infected eyes. Results indicate that pharmacokinetic parameters change in pathological conditions, which may help establish better treatment guidelines for endophthalmitis.

Minimum bactericidal concentrations of Propionibacterium acnes isolates from cases of chronic endophthalmitis

Six isolates of Propionibacterium acnes recovered from cases of chronic infectious endophthalmitis following extracapsular cataract extraction were tested for antibiotic susceptibility. All isolates were susceptible to penicillin, cefazolin, and vancomycin with a macrobroth dilution method. Minimum bactericidal concentrations testing at 72 h revealed that six of six isolates were killed by < or = 1.0 micrograms of vancomycin/ml, one of six isolates by < or = 1.0 micrograms of penicillin/ml, and zero of six isolates by < or = 1.0 micrograms cefazolin/ml.

Use of vancomycin in vitrectomy infusion solution and evaluation of retinal toxicity

The retinal toxicity of vancomycin in infusion solution used in vitrectomy and lensectomy was investigated in rabbit eyes by means of electroretinography and histologic study (light microscopy). Concentrations of 8 micrograms/ml, 16 micrograms/ml, and 32 micrograms/ml of vancomycin in balanced salt solution caused no abnormal ERG or histologic changes. However, ERG amplitude depression and abnormal histologic changes occurred when the concentration of 100 micrograms/ml of vancomycin was used.

Rural endophthalmitis

The antibiotic regimens recommended for empiric use in posttraumatic endophthalmitis are based on data collected from medical centers in large metropolitan areas. In rural areas, trauma resulting in endophthalmitis frequently involves injuries with perforating objects that are contaminated with organic matter. These rural cases therefore may not be comparable with endophthalmitis occurring after nonrural injuries. A 10-year retrospective analysis was performed to investigate the incidence of rural endophthalmitis as well as determine the type of causative organisms. Endophthalmitis developed in 24 (30%) of 80 patients with rural penetrating trauma, compared with 23 (11%) of 204 patients with nonrural penetrating trauma. Of 24 patients, Bacillus spp were isolated in 11 (46%), followed by gram-negative rods in 7, Staphylococcus epidermidis in 6, and streptococcal species in 5. In 10 (42%) of these 24 patients with rural trauma, more than one organism was isolated. Bacillus spp were involved in six (60%) of ten of these mixed infections. Based on these findings, the authors suggest an intravitreal regimen of gentamicin along with either vancomycin or clindamycin for the empiric therapy of rural endophthalmitis.

The treatment of postoperative endophthalmitis. Results of differing approaches to treatment

The authors treated 26 patients with postoperative endophthalmitis over a 4-year period, between 1983 and 1986. Nineteen patients were culture-positive and seven were culture-negative. All patients received intravitreal antibiotics as part of their treatment regimen. Culture-negative patients generally responded well to a single intravitreal antibiotic injection. Five of seven (71.4%) culture-positive patients who were treated with a single intravitreal antibiotic injection and no vitrectomy suffered either a recurrence of their infection or did not respond to treatment. Four of five patients who received a vitrectomy in addition to a single intravitreal antibiotic injection were cured of their infections; the one patient who received repeated intravitreal antibiotic injections alone and all six patients who received repeated intravitreal antibiotic injections in combination with vitrectomy were cured of their infections. Although the intravitreal injection of antibiotics provides an extremely high initial level of antibiotics inside the eye, a single intravitreal antibiotic injection may only partially treat bacterial endophthalmitis. In culture-negative cases, a single intravitreal injection of antibiotics appears to be sufficient treatment. In culture-positive cases, a higher cure rate is achieved with an aggressive approach which includes the use of repeated intravitreal antibiotic injections and/or vitrectomy.

Coagulase-negative staphylococcal endophthalmitis. Increase in antimicrobial resistance

The predicted sensitivities of common organisms guide initial antibiotic therapy in endophthalmitis. The authors suspected a change in the expected sensitivity of coagulase-negative staphylococci when three cases of endophthalmitis due to multiply resistant organisms failed to respond to intravitreal cefazolin and gentamicin. The authors reviewed 48 cases from 1982 to 1986, compared these with 28 cases from 1973 to 1981, they found increased resistance to gentamicin (35 versus 0%, P less than 0.05) and increased resistance to methicillin (27 versus 19%). Eight cases were resistant to both antibiotics, including the three clinical failures. Final vision was unrelated to antimicrobial resistance. Since cephalosporins may be ineffective clinically against methicillin-resistant staphylococci, concomitant gentamicin resistance may render intravitreal cefazolin and gentamicin inadequate for their treatment. No isolates were resistant to vancomycin. Vancomycin and aminoglycoside, used intravitreally in the initial management of endophthalmitis, would be anticipated to provide better coverage than cefazolin and aminoglycoside for endophthalmitis due to the staphylococci, as well as for infections due to streptococcal and bacillus species.

Microbial endophthalmitis resulting from ocular trauma

Twenty-seven cases of culture-positive endophthalmitis that developed after ocular trauma were reviewed. The intraocular culture specimens showed a virulent microbiologic spectrum with Bacillus sp as the most common isolate (8 eyes). The visual prognosis was poor, with only 22% of patients retaining 20/400 or better vision. This level of vision was achieved in 2 of 22 (9%) bacterial cases and in four of five (80%) fungal cases. Retinal detachment (5 cases) or retinal breaks (2 cases) at the time of the initial injury had a uniformly poor visual prognosis. Postoperative retinal detachment not associated with phthisis bulbi occurred in five eyes, three of which had successful retinal reattachment surgery. Delayed onset retinal detachment after successful initial management of traumatic endophthalmitis had a greater frequency of successful retinal reattachment surgery.

Treatment of experimental methicillin-resistant Staphylococcus epidermidis endophthalmitis with intravitreal vancomycin

Endophthalmitis remains a dreaded complication of intraocular surgery and penetrating eye trauma. Subconjunctival, topical, and systemic antibiotics have been largely ineffective in the treatment of endophthalmitis, whereas intravitreal antibiotics have proved efficacious. Methicillin-resistant Staphylococcus epidermidis has become an important pathogen in many infections, including endophthalmitis. Toxicity, clearance, and efficacy of intravitreal vancomycin were evaluated in the treatment of experimental methicillin-resistant S. epidermidis endophthalmitis. No evidence of retinal toxicity was found and therapeutic levels were demonstrated six days after injection. The treated rabbit eyes showed a marked beneficial effect when compared to the untreated eyes. If experience confirms the safety of intravitreal vancomycin in human eyes, vancomycin should be considered the drug of choice for methicillin-resistant S. epidermidis endophthalmitis.

The experimental and clinical use of intravitreal antibiotics to treat bacterial and fungal endophthalmitis

The experimental data involving the use of 14 antibacterial and two antifungal agents have been used to establish a rationale for the management of human endophthalmitis. Twelve cases of endophthalmitis treated under our supervision have been described in detail. The eventual visual outcome is related to two factors: (1) time interval between diagnosis and institution of adequate therapy, and (2) the severity of the organism and its ability to produce exotoxins and proteolytic enzymes. Eleven of 12 cases were cured with the recommended dosages of gentamicin and dexamethasone (400 mcg and 360 mcg, respectively). Eight of the 12 patients retained useful vision of 20/200 or better.